<!DOCTYPE html>
<html>
<head>
	<title>定位的盒子居中显示</title>
	<style type="text/css">
		body{
			margin: 0;
			padding: 0;
		}
		.box{
			height: 500px;
			background: #aaa;
			position: relative;
		}
		.nav{
			width: 960px;
			height: 60px;
			background: #666;
			position: absolute;;
			bottom: 0;
			left: 50%;
			margin-left: -480px;
		}
	</style>
</head>
<body>
	<div class="box">
		<div class="nav"></div>
	</div>
</body>
</html>